El Niño Gets a Boost from Climate Change: Unusual Activity in 20th Century

The weather system, El Niño, can affect rain and temperature conditions globally. It causes Atlantic hurricane activity to wane, rainfall in Hawaii to decrease and Pacific winter storms to shift southward. Now, though, it turns out that El Niño may be getting a bit of a boost--all thanks to climate change.

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El Niño, also known as the El Niño Southern Oscillation (ENSO), occurs when the Equatorial Pacific experiences unusually warm ocean temperatures. It's essentially the oscillation of the ocean-atmosphere system, which can have important consequences for weather around the globe. Needless to say, it's important to monitor this phenomenon, which is why the NOAA possesses a network of buoys in the area which measure temperature, currents and wind.

Since this weather system is greatly affected by and affects temperature, it's not surprising that researchers are interested in how climate change might impact the phenomenon. In order to better understand ENSO, researchers examined the tree ring record that revealed weather pattern activity over the past seven centuries. Tree rings are extremely good at recording weather conditions, revealing temperature and rainfall measurements. In all, the researchers compiled 2,222 tree ring chronologies from both the tropics and mid-latitudes in both hemispheres.

So what did they find? It turns out that ENSO was unusually active in the late 20th century compared to the past seven centuries. This seemed to indicate that ENSO was actually being affected by climate change and global warming conditions.

"In the year after a large tropical volcanic eruption, our record shows that the east-central tropical Pacific is unusual cool, followed by unusual warming on year later," said lead author, Jinbao Li, in a news release. "Like greenhouse gases, volcanic aerosols perturb the Earth's radiation balance. This supports the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming."

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The findings are crucial for future climate models, which may need to factor in ENSO for better predictions. In addition, it reveals that many current models underestimate the sensitivity to radiative perturbations in greenhouse gases.